Unrelated to the thread - do you use any email providers with a custom domain? If so, would you suggest them? Who are they?
With all the Big Corp asterisks, Microsoft Business Basic can be a pretty great deal at 6 USD/month. Solid reliability, aliases, (too many) config options, 1TB of OneDrive storage, cloud MS apps, etc.
Either now is probably a good choice.
I then used some other platform that was quite "old school" that is recommended here. The Mail Admin was very opinionated which lead to some mail being blocked. That wasn't cool.
I'm now with Migadu on the cheapest plan and it's been fine. Had a few outages here and there, but otherwise solid.
I'd happily rec Fastmail or Migadu.
other popular options are fastmail, migadu, and mxroute.